Mobile user terminal, mobile communication system, base station, and communication method

ABSTRACT

A mobile user terminal includes a receiver which receives a signal, and a processor which measures downlink channel quality based on the signal and does not transmit downlink channel quality information and an uplink pilot signal simultaneously at a period which the mobile user terminal is a state of transmission off in an intermittent fashion.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/172,239, filed on Jun. 29, 2011, now pending, which is a continuationof U.S. patent application Ser. No. 11/892,611 filed on Aug. 24, 2007,now U.S. Pat. No. 8,064,937 B2, which claims the benefit of priority ofJapanese Patent Application No. 2006-254525, filed on Sep. 20, 2006, theentire contents of each are herein incorporated by reference. Thispresent application also relates to U.S. patent application Ser. No.12/786,064 filed on May 24, 2010, now U.S. Pat. No. 7,974,649 B2.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile communication terminal, mobilecommunication system, base station, and a communication method for useby them, and more particularly to a control technique for controllingthe transmission timing of control information to be transferred betweena mobile communication terminal and a base station.

2. Description of the Related Art

FIG. 1 shows the configuration of a UMTS (Universal MobileTelecommunications System), a mobile communication system standardizedby the 3GPP (3rd Generation Partnership Project). The radiocommunication system 1 comprises a radio access network N1 called aUTRAN (Universal Terrestrial Radio Access Network), a circuit switchingcore network N2, which connects the radio access network N1 and a publicswitch telephone network N3 to provide radio switched services, and apacket switching core network N4, which connects the radio accessnetwork N1 and an Internet protocol (IP) network N5 to provide packetswitched services.

The radio access network N1 comprises base stations BSs and radionetwork controllers 2 (RNCs) for controlling the BSs, and is responsiblefor transferring user information, such as voice and packets from mobileuser terminals (UEs) to core networks N2 and N4 and vice versa and forallocating radio resources necessary for communications between them.

The circuit switching core network N2 comprises a mobile switchingcenter (MSC) 3 and a gateway mobile switching center (GMSC) 4, and isresponsible for establishing communication links between terminals bycircuit switching.

The packet switching core network N4 comprises: a serving GPRS supportnode (SGSN) 5, which keeps track of the position of each mobile userterminal UE accessing the packet switched domain and transfers usertraffic between a gateway GPRS support node 6 described below, and theradio access network N1; and the gateway GPRS support node (GGSN) 6,which controls the connection between the mobile communication system 1and the external IP network N5 in accordance with a connection requestfrom the mobile user terminal UE, the packet switching core network N4thus providing IP connections between mobile user terminals UEs orbetween mobile user terminals (UEs) and an external IP network.

The radio communication system 1 further includes a home locationregister (HLR) 7 and an authentication center (AUC) 8, which performsauthentication and manages authentication and other confidentialinformation.

When a mobile user terminal UE is connected to a base station BS, themobile user terminal (UE) intermittently transmits control informationto the base station (BS), i.e., downlink quality information (downlinkCQI) that indicates the channel quality of a downlink or a downstreamchannel along which signals are transmitted from the base station (BS)to the mobile user terminal (UE), and an uplink pilot signal to be usedfor measuring channel quality of an uplink or an upstream channel alongwhich signals are transmitted from the mobile user terminal (UE) to thebase station (BS).

The mobile user terminal (UE) receives a downlink pilot signaltransmitted via a common pilot channel from the base station (BS), andmeasures the channel quality of the downlink propagation path. Theresult of the measurement is transmitted as downlink quality informationto the base station (BS). When downstream traffic occurs from the basestation (BS) to the mobile user terminal (UE), the base station (BS)thus supplied with downlink quality information can transmit downstreamtraffic by selecting the transmission format (modulation method,error-correction method, code rate, etc.) that best matches theconditions of the downlink propagation path.

The mobile user terminal (UE) transmits, the upstream pilot signal tothe base station (BS) via an upstream dedicated control channelallocated to each individual terminal. The base station (BS) measuresthe channel quality of the uplink propagation path by measuring thereception condition of the upstream pilot signal. By measuring thechannel quality of the uplink propagation path, the base station (BS)can determine the transmission format (modulation method,error-correction method, code rate, etc.) that best matches theconditions of the uplink propagation path.

In the prior art mobile communication system, the transmission timingand carrier frequency of the downlink quality information and thetransmission timing and carrier frequency of the uplink pilot signalhave been set independent of each other, and this has led to increasedpower consumption and increased processing complexity of the transmittercircuit in the mobile user terminal (UE), and thus an increased burdenon the mobile user terminal (UE). The reason will be described withreference to FIG. 2.

FIG. 2 is a time chart showing a prior art example of how downlinkquality information and uplink pilot signal are transmitted. In FIG. 2,the uplink pilot signal (Pilot) is transmitted at times t1 to t2 and t6to t7, and irrespective of the timing, downlink quality information(CQI) is transmitted at times t2 to t3, t4 to t5, and t8 to t9.

When transmitting the downlink quality information and uplink pilotsignal at such times, the mobile user terminal (UE) has to drive itstransmitter circuit at each transmission timing.

Specifically, in the 3.9-generation mobile communication architecture(3GPP LTE), standardization of which is currently underway, a standbystate called the MAC-Dormant state is provided as a state in which themobile user terminal (UE) can take on, in order to enable datatransmission/reception to be initiated upon occurrence of traffic. Inthe MAC-Dormant state, data transmission/reception is not performed, butthe mobile user terminal (UE) transmits the downlink quality informationand uplink pilot signal in an intermittent fashion.

In the MAC-Dormant state, when neither the downlink quality informationnor the uplink pilot signal is transmitted, power is not supplied to theamplifier circuit in the output stage of the transmitter circuit, andthe amplifier circuit is driven only intermittently, thereby reducingpower consumption. FIG. 3 shows a state transition diagram for themobile user terminal (UE) as defined by the 3.9-generation mobilecommunication architecture. In FIG. 3, LTE-Active state indicates acommunication state, and the MAC-Active state contained thereinindicates a state in which communication is proceeding continuously,while the MAC-Dormant state indicates a state in which controlinformation such as described above is transmitted and received in anintermittent fashion. Conversely, an LTE-Idle state indicates a standbystate in which no control information is transmitted or received, andthe LTE-Detached state indicates a state in which the power of themobile user terminal (UE) is OFF.

When driving the amplifier circuit in an intermittent fashion, theamplifier circuit must be energized for a predetermined standby time,before the input of a transmit signal, in order to stabilize the outputcharacteristics of the amplifier circuit. During this standby time, theamplifier circuit does not amplify the transmit signal, and consumespower unnecessarily. As a result, if the transmission timing of thedownlink quality information is spaced apart from the transmissiontiming of the uplink pilot signal, the amount of power unnecessarilyconsumed increases, because standby time occurs before each transmissiontiming.

In the 3.9-generation mobile communication architecture, bandwidths of1.25 MHz, 2.5 MHz, 10 MHz, 15 MHz, and 20 MHz can be used in addition tothe 5-MHz bandwidth used in the current third generation mobilecommunication systems. FIG. 2 shows a case where the mobile userterminal (UE) conforming to such 3.9-generation mobile communicationarchitecture, transmits the uplink pilot signal using a 20-MHz bandwidthchannel and downlink quality information using a 5-MHz bandwidthchannel.

When changing the transmit signal frequency, the mobile user terminal(UE) optimizes the frequency characteristic of the amplifier circuit inaccordance with the carrier frequency in order to enhance powerefficiency. The frequency characteristic of the amplifier circuit isvaried by changing the bias to be applied to the active device used inthe amplifier circuit. However, there is a limit to how fast the activedevice can follow the change in bias, and when the amount of bias islarge, the amount of delay with which the frequency characteristic ofthe active device changes in response to the change in the bias becomeslarge.

As a result, when the amount of change of the transmit signal frequencyis large, the bias to the active device must be controlled by takinginto account the amount of delay with which the frequency characteristicof the active device changes, and this increases the processingcomplexity of the transmitter circuit within the mobile user terminal(UE). The same problem also occurs when the frequency bandwidth of thetransmit signal greatly changes as shown in FIG. 2.

SUMMARY OF THE INVENTION

In view of the above problem, in a mobile communication system in whicha mobile user terminal transmits downlink quality information and anuplink pilot signal to a base station, it is an object of the presentinvention to reduce the burden that has been imposed on the mobile userterminal because the transmission timing and carrier frequency of thedownlink quality information and the transmission timing and carrierfrequency of the uplink pilot signal have been set independent of eachother.

That is, it is an object of the present invention to reduce powerconsumption by reducing the time that the amplifier circuit foramplifying the downlink quality information signal and the uplink pilotsignal within the mobile user terminal has to be energized when themobile user terminal transmits these control signals in an intermittentfashion.

Furthermore, it is also an object of the present invention to preventthe processing complexity of the transmitter circuit from increasing,because the carrier frequency used for the transmission of the downlinkquality information and the carrier frequency used for the transmissionof the uplink pilot signal greatly differ from each other, when themobile user terminal transmits the downlink quality information and theuplink pilot signal.

To achieve the above object, the present invention synchronizes thetransmit time of the downlink quality information and the transmit timeof the uplink pilot signal relative to each other. By thus synchronizingthe transmit times, it is possible to transmit the downlink qualityinformation and the uplink pilot signal at the same time or insuccessive time periods. This reduces the number of times that theamplifier circuit provided in the output stage of the transmittercircuit of the mobile user terminal has to be energized. Since the timethat the amplifier circuit has to be energized prior to the transmissionof the signal can be reduced, power consumption is reduced, and theburden on the mobile user terminal is also reduced.

Furthermore, in the present invention, the downlink quality informationand the uplink pilot signal are transmitted by using the same carrierfrequency or by using adjacent carrier frequencies selected from among aplurality of carrier frequencies preassigned to the mobile userterminal. By setting the carrier frequency in this manner, it ispossible to reduce the amount of bias control for the amplifier circuitprovided in the output stage of the transmitter circuit of the mobileuser terminal, and as a result, processing complexity of the transmittercircuit can be prevented from increasing, and the burden on the mobileuser terminal is thus alleviated.

According to a first mode of the present invention, there is provided amobile user terminal for use in a mobile communication system, in whichthe mobile user terminal measures downlink channel quality, andtransmits downlink quality information indicating the measured downlinkchannel quality and an uplink pilot signal to be used for measuringuplink channel quality in an intermittent fashion to a base station.

The mobile user terminal comprises a transmit time control unit, whichsynchronizes the transmit time of the downlink quality information andthe transmit time of the uplink pilot signal relative to each other, andthus the transmit time of the downlink quality information and uplinkpilot signal to be transmitted in an intermittent fashion aresynchronized relative to each other.

The mobile user terminal may comprise a radio transmitting unit, whichtransmits the downlink quality information and the uplink pilot signalby using the same carrier frequency or by using adjacent carrierfrequencies selected from among a plurality of preassigned carrierfrequencies.

The transmit time control unit may set the transmission cycle for one ofthe downlink quality information and the uplink pilot signal to be anintegral multiple of the transmission cycle of the other one thereof.Alternatively, the transmit time control unit may control the transmittime so that the downlink quality information and the uplink pilotsignal are transmitted at the same time or in succession.

The radio transmitting unit may transmit both the downlink qualityinformation and the uplink pilot signal by using some carrierfrequencies clustered in a localized manner and selected from among aplurality of carrier frequencies preassigned within a given frequencyband. Alternatively, the radio transmitting unit may transmit both thedownlink quality information and the uplink pilot signal by using somecarrier frequencies contained in a distributed manner within a givenfrequency band and selected from among a plurality of carrierfrequencies preassigned within the given frequency band. In this case,the radio transmitting unit may transmit the downlink qualityinformation and the uplink pilot signal in an intermittent fashion inaccordance with the transmit time controlled by the transmit timecontrol unit.

According to a second mode of the present invention, there is provided amobile communication system which comprises the mobile user terminal ofthe first mode of the present invention, wherein the downlink qualityinformation and the uplink pilot signal are transmitted in anintermittent fashion from the mobile user terminal to a base station.

When the mobile user terminal transmits the uplink pilot signal and thedownlink quality information at the same time or at times close to eachother by using the same frequency or adjacent frequencies, the uplinkpilot signal can be used as a reference channel for channel estimationfor the downlink quality information.

Accordingly, the base station used in this system may include a channelestimating unit, which performs channel estimation for a channel usedfor transmission of the downlink quality information, by using theuplink pilot signal received from the mobile user terminal as areference channel.

According to a third mode of the present invention, there is provided abase station to be used in the mobile communication system of the secondmode of the present invention. The base station includes a channelestimating unit, which performs channel estimation for a channel usedfor transmission of the downlink quality information, by using theuplink pilot signal received from the mobile user terminal as areference channel.

According to a fourth mode of the present invention, there is provided acommunication method in which downlink channel quality is measured at amobile user terminal, and downlink quality information indicating themeasured downlink channel quality and an uplink pilot signal to be usedfor measuring uplink channel quality are transmitted from the mobileuser terminal to a base station.

In this communication method, the downlink quality information and theuplink pilot signal are transmitted in an intermittent fashion from themobile user terminal to the base station. The mobile user terminalsynchronizes the transmit time of the downlink quality information withthe transmit time of the uplink pilot signal. The mobile user terminalmay transmit the downlink quality information and the uplink pilotsignal by using the same carrier frequency or by using adjacent carrierfrequencies selected from among a plurality of preassigned carrierfrequencies.

When synchronizing the transmit time of the downlink quality informationand the transmit time of the uplink pilot signal relative to each other,the transmission cycle for either one of the downlink qualityinformation and the uplink pilot signal may be set to an integralmultiple of the transmission cycle for the other, or alternatively, thedownlink quality information and the uplink pilot signal are transmittedat the same time or in succession.

Both the downlink quality information and the uplink pilot signal may betransmitted by using carrier frequencies clustered in a localized mannerand selected from among a plurality of carrier frequencies preassignedwithin a given frequency band, or may be transmitted by using carrierfrequencies contained in a distributed manner within the given frequencyband and selected from among the plurality of carrier frequenciespreassigned within the given frequency band.

Furthermore, in this method, channel estimation for a channel used fortransmission of the downlink quality information may be performed in thebase station by using the uplink pilot signal received from the mobileuser terminal as a reference channel.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from thedescription as set out below with reference to the accompanyingdrawings, wherein:

FIG. 1 is a diagram showing the configuration of a mobile communicationsystem standardized by the 3GPP;

FIG. 2 is a time chart showing a prior art example of how downlinkquality information and an uplink pilot signal are transmitted;

FIG. 3 is a state transition diagram for a mobile user terminal (UE) asdefined by the 3.9-generation mobile communication architecture;

FIG. 4 is a schematic block diagram showing the configuration of a basestation according to an embodiment of the present invention;

FIG. 5 is a schematic block diagram showing the configuration of amobile user terminal according to the embodiment of the presentinvention;

FIG. 6 is a flowchart illustrating the operation of the mobile userterminal shown in FIG. 5 when transmitting the downlink qualityinformation and the uplink pilot;

FIG. 7 is a time chart for the downlink pilot signal and broadcastinformation;

FIG. 8 is a time chart (part 1) showing how the downlink qualityinformation and the uplink pilot signal are transmitted by the mobileuser terminal of the present invention;

FIG. 9 is a time chart (part 2) showing how the downlink qualityinformation and the uplink pilot signal are transmitted by the mobileuser terminal of the present invention;

FIG. 10A is a diagram showing a first configuration example of a radiotransmitting unit in the mobile communication terminal shown in FIG. 5;

FIG. 10B is a diagram showing a second configuration example of theradio transmitting unit in the mobile user terminal shown in FIG. 5;

FIG. 11 is a time chart (part 1) showing how the downlink qualityinformation and the uplink pilot signal are transmitted out in adistributed manner from the mobile user terminal of the presentinvention;

FIG. 12 is a time chart (part 2) showing how the downlink qualityinformation and the uplink pilot signal are transmitted out in adistributed manner from the mobile user terminal of the presentinvention;

FIG. 13 is a time chart (part 1) showing how the downlink qualityinformation and the uplink pilot signal are transmitted out in alocalized manner from the mobile user terminal of the present invention;

FIG. 14 is a time chart (part 2) showing how the downlink qualityinformation and the uplink pilot signal are transmitted out in alocalized manner from the mobile user terminal of the present invention;

FIG. 15 is a time chart (part 1) showing how the downlink qualityinformation and the uplink pilot signal are transmitted out when theamount of data to be transmitted differs between them;

FIG. 16 is a time chart (part 2) showing how the downlink qualityinformation and the uplink pilot signal are transmitted out when theamount of data to be transmitted differs between them;

FIG. 17 is a time chart (part 3) showing how the downlink qualityinformation and the uplink pilot signal are transmitted out when theamount of data to be transmitted differs between them;

FIG. 18 is a time chart (part 4) showing how the downlink qualityinformation and the uplink pilot signal are transmitted out when theamount of data to be transmitted differs between them;

FIG. 19A is a diagram showing a first configuration example of the radioreceiving unit in the base station shown in FIG. 4 when the radiotransmitting unit is configured to perform channel estimation for thedownlink quality information;

FIG. 19B is a diagram showing a second configuration example of theradio receiving unit in the base station shown in FIG. 4 when the radiotransmitting unit is configured to perform channel estimation for thedownlink quality information; and

FIG. 20 is a flowchart showing the channel estimation operation for thedownlink quality information performed in the base station shown in FIG.4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be described indetail below while referring to the attached figures. FIG. 4 is aschematic block diagram showing the configuration of a base stationaccording to an embodiment of the present invention, and FIG. 5 is aschematic block diagram showing the configuration of a mobile userterminal according to the embodiment of the present invention. Theconfiguration of the mobile user system according to the embodiment ofthe present invention is generally the same as that of the mobilecommunication system previously described with reference to FIG. 1, andtherefore, the description thereof will not be repeated here. The mobilecommunication system of the present invention supports the3.9-generation mobile communication architecture, and the mobile userterminal (UE) shown in FIG. 5 can take on any one of the states shown inthe state transition diagram of FIG. 3.

The base station (BS) shown in FIG. 4 comprises a transmitting antenna101 and a radio transmitting unit 102 for transmitting radio signalsdownstream to the mobile user terminal UE. The downstream radio signalsinclude various kinds of control information that are transmitted over adownstream dedicated control channel, a downstream common controlchannel, and a common pilot channel, respectively.

The downstream dedicated control channel is a dedicated control channel,which is assigned to each individual mobile user terminal (UE) for thetransmission of control information from the base station (BS) to theindividual mobile user terminal (UE), the downstream common controlchannel is a control channel over which the base station (BS) transmitscontrol information to all mobile user terminals (UEs) simultaneously,and the common pilot channel is a control channel over which the basestation (BS) transmits the downlink pilot signal to all mobile userterminals (UEs) simultaneously.

The base station (BS) includes: a downstream dedicated control channelprocessing unit 103 and a downstream common control channel processingunit 104 which perform processing for the transmission of the signalsover the downstream dedicated control channel and the downstream commoncontrol channel, respectively, and a common pilot channel processingunit 105, which outputs the downlink pilot signal to be transmitted overthe common pilot channel.

The base station (BS) further includes a receiving antenna 111 and aradio receiving unit 112 for receiving upstream radio signals from themobile user terminal (UE). The upstream radio signals include variouskinds of control information that are transmitted over a first andsecond upstream control channel, respectively.

The first and second upstream control channels are control channels overwhich each individual mobile user terminal (UE) can transmit theircontrol information. Such control channels may be configured as sharedcontrol channels which are assigned, from among common physical channelresources, to each individual mobile user terminal (UE) by changing thetime slot, frequency, or spreading code for each mobile user terminal(UE), or may be configured as dedicated control channels that areindividually assigned to each different mobile user terminal (UE).

The base station (BS) includes a first upstream control channelreceiving unit 113 and a second upstream control channel receiving unit114, which perform processing for the reception of control informationtransmitted over the first and second upstream control channels,respectively.

The base station (BS) further includes a transmit time informationgenerating unit 106, which creates transmit time information forspecifying the transmit time at which the mobile user terminal (UE)should transmit the downlink quality information or the uplink pilotsignal. The transmit time information generating unit 106 supplies thetransmit time information to the downstream dedicated control channelprocessing unit 103, which transmits the transmit time information tothe mobile user terminal (UE) over the downstream dedicated controlchannel. A method of how the transmit time of the downlink channelquality information or the uplink pilot signal is specified by thetransmit time information will be described later by way of example.Here, the transmit time information may be created, not in the basestation (BS), but in its serving radio network controller 2 shown inFIG. 1. In which, the transmit time information generating unit 106 isprovided in the radio network controller 2, not in the base station(BS).

Referring back to FIG. 4, the base station (BS) further includes abroadcast information generating unit 107, which creates broadcastinformation. The broadcast information contains a frame numberindicating the ordinal position of the frame that carries the downlinkpilot signal currently being transmitted from the common pilot channelprocessing unit 105. The broadcast information generating unit 107supplies the broadcast information to the downstream common controlchannel processing unit 104, which transmits the broadcast informationto the mobile user terminal (UE) over the downstream common controlchannel.

The mobile user terminal (UE) shown in FIG. 5 comprises: a receivingantenna 201; a radio receiving unit 202 for receiving downstream radiosignals from the base station BS; a common pilot channel receiving unit203, which performs processing for the reception of the downlink pilotsignal transmitted over the common pilot channel; a downstream dedicatedcontrol channel receiving unit 204, which performs processing for thereception of the control information transmitted over the downstreamdedicated control channel; and a downstream common control channelreceiving unit 205, which performs processing for the reception of thecontrol information transmitted over the downstream common controlchannel.

The mobile user terminal (UE) further comprises: a transmitting antenna211; a radio transmitting unit 212 for transmitting upstream radiosignals to the base station BS; a first upstream control channelprocessing unit 213, which performs processing for the transmission ofthe signal over the first upstream control channel; and a secondupstream control channel processing unit 214, which performs processingfor the transmission of the signal over the second upstream controlchannel.

The mobile user terminal (UE) further includes a CQI generating unit206, a pilot generating unit 215, a frame/slot number detecting unit207, a transmit time detecting unit 208, and a transmit time controlunit 216.

The CQI generating unit 206 measures quality metrics such as the SIR(Signal to Interference Ratio) of the common pilot channel, etc., thatindicate the downlink channel quality, generates downlink qualityinformation containing such quality metrics, and supplies it to thefirst upstream control channel processing unit 213. The downlink qualityinformation is transmitted to the base station (BS) over the firstupstream control channel.

The pilot generating unit 215 generates the uplink pilot signal that thebase station (BS) uses to measure the uplink channel quality, andsupplies the pilot signal to the second upstream control channelprocessing unit 214. The uplink pilot signal is transmitted to the basestation (BS) over the second upstream control channel.

The frame/slot number detecting unit 207 detects the frame number of thecurrently received downlink pilot contained in the broadcast informationreceived by the downstream common control channel receiving unit 205.The frame/slot number detecting unit 207 also detects the slot number ofthe current time slot by measuring the time that has elapsed since thecommon pilot channel receiving unit 203 began to receive the downlinkpilot of the current frame.

The transmit time detecting unit 208 detects the transmit timeinformation from the control information transmitted over the downstreamdedicated control channel and received by the downstream dedicatedcontrol channel receiving unit 204.

The transmit time control unit 216 receives the transmit timeinformation from the transmit time detecting unit 208 and the framenumber and slot number of the current time slot from the frame/slotnumber detecting unit 207. Then, by referring to the transmit timeinformation received from the transmit time detecting unit 208, thetransmit time control unit 216 determines whether the current time slotis a time slot for signal transmission, i.e., the slot for thetransmission of the downlink channel quality information or the uplinkpilot signal.

Each time it is determined that the current time slot is the slot fortransmitting the downlink channel quality information, the transmit timecontrol unit 216 outputs a transmission permit signal permitting thefirst upstream control channel processing unit 213 to transmit thedownlink quality information, and each time it is determined that thecurrent time slot is the slot for transmitting the uplink pilot signal,the transmit time control unit 216 outputs a transmission permit signalpermitting the second upstream control channel processing unit 214 totransmit the uplink pilot signal. With this operation, the transmit timecontrol unit 216 allows the downlink quality information and the uplinkpilot signal to be transmitted in an intermittent fashion, whilemaintaining synchronization between their transmit times.

FIG. 6 is a flowchart illustrating the operation of the mobile userterminal (UE) shown in FIG. 5 when transmitting the downlink qualityinformation and the uplink pilot.

In step S1, the downstream dedicated control channel receiving unit 204receives via the downstream dedicated control channel the transmit timeinformation that was generated by the transmit time informationgenerating unit 106 in the base station (BS) and that specifies thetransmit time for the downlink quality information or the uplink pilotsignal. The transmit time detecting unit 208 detects the transmit timeinformation specifically intended for the mobile user terminal UE fromamong the signals that the downstream dedicated control channelreceiving unit 204 received via the downstream dedicated controlchannel.

The transmit time information is information by reference to which thetransmit time control unit 216 determines the times at which thetransmission permit signal for the downlink quality information and thetransmission permit signal for the uplink pilot signal should be outputto the first and second upstream control channel processing units 213and 214, respectively. The transmit time information may provide, forexample, a frame number and a slot number that specify the time slot fortransmitting either or both the downlink quality information and theuplink pilot signal.

If for example, the transmission cycle of the downlink qualityinformation and the transmission cycle of the uplink pilot signal arepredetermined, the frame number containing the time slot assigned to themobile user terminal (UE) as the transmit time may be specified by thenumber, n, of frames corresponding to the transmission cycle and theremainder resulting from the division of the frame number by the number,n, of frames.

When the common pilot channel receiving unit 203 receives the downlinkpilot signal in step S2, the CQI generating unit 206 generates thedownlink channel quality information. The common pilot channel receivingunit 203 also supplies the downlink pilot signal to the frame/slotnumber detecting unit 207.

In step S3, the downstream common control channel receiving unit 205receives via the downstream common control channel the broadcastinformation that was generated by the broadcast information generatingunit 107 in the base station BS.

Then, in step S4, the frame/slot number detecting unit 207 detects theframe number of the currently received downlink pilot signal from thebroadcast information. Further, the frame/slot number detecting unit 207detects the slot number of the current time slot.

FIG. 7 is a time chart for the downlink pilot signal and the broadcastinformation. The downlink pilot signal flowing on the common pilotchannel has a signal pattern which repeats a known bit pattern for eachframe. The broadcast information contains the frame number of thecurrently transmitted downlink pilot signal. Since the bit pattern ofthe downlink pilot signal is known, the frame/slot number detecting unit207 can determine the start time of the current frame by matching thecurrently received downlink pilot signal against the known bit pattern.

As shown, one frame is made up of a predetermined number of slots (mslots in the illustrated example) each of a known duration. Theframe/slot number detecting unit 207 can determine the slot number ofthe current time slot by determining the time elapsed from the starttime of the current frame.

Referring back to FIG. 6, the transmit time control unit 216 determinesin step S5 whether the current time slot whose frame number and slotnumber were detected in step S4 coincides with the transmit time thatthe transmit time information detected in step S1 specifies for theuplink pilot signal.

For example, when the transmit time information designates the framenumber and slot number of the time slot for transmitting the uplinkpilot signal, the transmit time control unit 216 determines whether thecombination of the frame number and slot number of the time slot thusdesignated matches the combination of the frame number and slot numberof the current time slot. If they match, it is determined that thecurrent time slot is the transmit time, but if they do not match, it isdetermined that the current time slot is not the transmit time.

On the other hand, when the transmit time information designates onlythe frame number and slot number of the time slot for transmitting thedownlink quality information, the transmit time control unit 216determines whether the combination of the frame number and slot numberof the current time slot satisfies a prescribed relationship withrespect to the combination of the frame number and slot number of thetime slot thus designated. If they satisfy the prescribed relationship,it is determined that the current time slot is the transmit time, but ifthey do not satisfy the prescribed relationship, it is determined thatthe current time slot is not the transmit time.

Various relationships can be employed for the prescribed relationship.For example, the frame number/slot number combination is identical, orthe time slot for transmitting the uplink pilot signal is advanced ordelayed by a prescribed number of slots with respect to the time slotfor transmitting the downlink quality information.

Based on the time required to transmit the downlink quality informationand the time required to transmit the uplink pilot signal, the transmittime control unit 216 may determine the transmit time of the uplinkpilot signal so that the uplink pilot signal and the downlink qualityinformation which is transmitted in the specified time slot aretransmitted in succession.

If it is determined in step S5 that the time slot coincides with thetransmit time for the uplink pilot signal, the transmit time controlunit 216 in step S6 outputs the transmission permit signal permittingthe second upstream control channel processing unit 214 to transmit theuplink pilot signal. If the transmit time control unit 216 determines instep S5 that the time slot does not coincide with the transmit time forthe uplink pilot signal, the process proceeds to step S7.

In step S7, the transmit time control unit 216 determines whether thecurrent time slot whose frame number and slot number were detected instep S4 coincides with the transmit time that the transmit timeinformation detected in step S1 specifies for the downlink qualityinformation.

For example, when the transmit time information designates the framenumber and slot number of the time slot for transmitting the downlinkquality information, the transmit time control unit 216 determineswhether the combination of the frame number and slot number of the timeslot thus designated matches the combination of the frame number andslot number of the current time slot. If they match, it is determinedthat the current time slot is the transmit time, but if they do notmatch, it is determined that the current time slot is not the transmittime.

On the other hand, for example, when the transmit time informationdesignates only the frame number and slot number of the time slot fortransmitting the uplink pilot signal, the transmit time control unit 216determines whether the combination of the frame number and slot numberof the current time slot satisfies the prescribed relationship withrespect to the combination of the frame number and slot number of thetime slot thus designated; if they satisfy the prescribed relationship,it is determined that the current time slot is the transmit time, but ifthey do not satisfy the prescribed relationship, it is determined thatthe current time slot is not the transmit time.

Based on the time required to transmit the downlink quality informationand the time required to transmit the uplink pilot signal, the transmittime control unit 216 may determine the transmit time of the downlinkquality information so that the downlink quality information and theuplink pilot signal which is transmitted in the specified time slot aretransmitted in succession.

If it is determined in step S7 that the time slot coincides with thetransmit time for the downlink quality information, the transmit timecontrol unit 216 in step S8 outputs the transmission permit signalpermitting the first upstream control channel processing unit 213 totransmit the downlink quality information.

By operating in accordance with the flowchart shown in FIG. 6, themobile user terminal (UE) can synchronize the transmit time of thedownlink quality information and the transmit time of the uplink pilotsignal relative to each other. For example, when the time required totransmit the uplink pilot signal (Pilot) and the time required totransmit the downlink quality information (CQI) are known, the transmittime control unit 216 synchronizes the transmit time t2 of the downlinkquality information relative to the transmit time t1 of the uplink pilotsignal so that the transmit period t2 to t3 for the downlink qualityinformation immediately follows the transmit period t1 to t2 for theuplink pilot signal, as shown in FIG. 8.

In the example shown in FIG. 8, the uplink pilot signal is transmittedduring time periods t1 to t2 and t4 to t5, and downlink qualityinformation is transmitted during time periods t2 to t3 and t5 to t6using the same frequency band as the uplink pilot signal, during timeperiod t3 to t4, the signal transmission from the mobile user terminal(UE) is off. Here, the transmission cycle of the uplink pilot signal isthe same as that of the downlink quality information.

In the example of FIG. 8, since the radio transmitting unit 212transmits the uplink pilot signal and the downlink quality informationusing the same frequency band, upstream control channels that use thesame frequency band but use different times or spreading codes may beassigned to the first upstream control channel and the second upstreamcontrol channel for transmitting the respective signals, or the firstupstream control channel and the second upstream control channel may beassigned as the same upstream control channel.

Next, in the example shown in FIG. 9 for the transmission of thedownlink quality information and the uplink pilot signal, the transmittime control unit 216 synchronizes the transmit time of the downlinkquality information relative to the transmit time of the uplink pilotsignal so that the transmit time of the downlink quality informationcoincides with the transmit time of the uplink pilot signal.

In the example of FIG. 9, both the downlink quality information and theuplink pilot signal are transmitted together during time periods t1 tot2 and t3 to t4, during time period t2 to t3, the signal transmissionfrom the mobile user terminal (UE) is off. Here, the transmission cycleof the uplink pilot signal is the same as that of the downlink qualityinformation.

In the example of FIG. 9, the radio transmitting unit 212 transmits theuplink pilot signal and the downlink quality information using differentfrequency bands. To prevent the processing complexity of the radiotransmitting unit 212 from increasing as earlier described as a resultof increased difference between the transmission frequency of onecontrol information and that of the other control information, the radiotransmitting unit 212 assigns adjacent carrier frequencies for thetransmission of the uplink pilot signal and the downlink qualityinformation from among several carrier frequencies assigned to themobile user terminal (UE).

A multi-carrier transmitter circuit, such as an orthogonal frequencydivision multiplexing (OFDM) transmitter, which transmits signals onmultiple carrier frequencies may be employed as the radio transmittingunit 212. The radio transmitting unit 212 then may transmit either oneor both of the uplink pilot signal and the downlink quality informationin parallel on multiple carrier frequencies. FIGS. 10A and 10B arediagrams each showing an example of the radio transmitting unit 212configured as an OFDM transmitting circuit.

As shown in FIGS. 10A and 10B, the radio transmitting unit 212 includes:serial-parallel conversion circuits 230 and 231, which convert theuplink pilot signal and the downlink quality information respectivelyoutput from the first and second upstream control channel processingunits 213 and 214 into parallel signals; an inverse Fourier transformcircuit 234, which applies an inverse Fourier transform to the parallelsignals converted by the serial-parallel conversion circuits 230 and231; digital-to-analog conversion circuits 235 and 236, which convertthe digital quadrature signals output from the inverse Fourier transformcircuit 234 into analog quadrature signals; a quadrature modulator(QMOD) 237, which quadrature-modulates the analog quadrature signals;and a frequency conversion circuit 238, which converts thequadrature-modulated transmit signal into a radio frequency signal. Inthe block diagrams of FIGS. 10A and 10B, only the portions necessary fortransmitting the uplink pilot signal and the downlink qualityinformation are shown for, however the radio transmitting unit 212further includes component elements necessary for transmission of othercontrol signals, packet data, and voice data.

The radio transmitting unit 212 shown in FIG. 10A includes a switch 239,which under the control of the first and second upstream control channeltransmission permit signals output from the transmit time control unit216, operates in such a manner that, during the transmit time of thefirst upstream control channel, the output of the serial-parallelconversion circuit 230 that takes the input signal from the firstupstream control channel processing unit 213 and converts it into aparallel signal is coupled to an input terminal of the inverse Fouriertransform circuit 234 and, during the transmit time of the secondupstream control channel, the output of the serial-parallel conversioncircuit 231 that takes the input signal from the second upstream controlchannel processing unit 214 and converts it into a parallel signal iscoupled to the same input terminal of the inverse Fourier transformcircuit 234. Therefore, the inverse Fourier transform circuit 234assigns the same frequency band to the first and second upstream controlchannels, so that the uplink pilot signal and the downlink qualityinformation are transmitted using carriers of the same frequency.

FIG. 11 is a time chart showing how the uplink pilot signal and thedownlink quality information are transmitted out from the radiotransmitting unit 212 shown in FIG. 10A. As shown, the uplink pilotsignal is divided between multiple carrier frequencies and transmittedin parallel on the multiple carrier frequencies, and the downlinkquality information also is divided between multiple carrier frequenciesand transmitted in parallel on the multiple carrier frequencies.Transmit times t1 and t2 of these control signals are synchronizedrelative to each other so that the transmit period t1 to t2 fortransmitting the uplink pilot signal is immediately followed by thetransmit period t2 to t3 for transmitting the downlink qualityinformation, and the uplink pilot signal and the downlink qualityinformation are transmitted using the carriers of the same frequency.

In the transmission method shown in FIG. 11, the downlink qualityinformation and the uplink pilot signal are each transmitted out in aso-called distributed manner in order to reduce the effect of noise onthe entire signal if noise occurs in a portion of the frequency band.That is, the inverse Fourier transform circuit 234 selects carrierfrequencies distributed among the plurality of carrier frequencies lyingwithin a given frequency band assigned to the mobile user terminal (UE),and assigns selected carrier frequencies for the transmission of thedownlink quality information and the uplink pilot signal.

In the radio transmitting unit 212 shown in FIG. 10B, the output signalof the serial-parallel conversion circuit 230 and the output signal ofthe serial-parallel conversion circuit 231 are coupled to differentinput terminals of the inverse Fourier transform circuit 234. As aresult, the uplink pilot signal and the downlink quality information aretransmitted using carriers of different frequencies, and these controlsignals can be transmitted at the same time in the same manner aspreviously described with reference to FIG. 9.

FIG. 12 is a time chart showing how the uplink pilot signal and thedownlink quality information are transmitted out from the radiotransmitting unit 212 shown in FIG. 10B. As shown, the uplink pilotsignal is divided between multiple carrier frequencies and transmittedin parallel on the multiple carrier frequencies, and the downlinkquality information also is divided between multiple carrier frequenciesand transmitted in parallel on the multiple carrier frequencies. Here,the uplink pilot signal and the downlink quality information aretransmitted at the same time. Further, the uplink pilot signal and thedownlink quality information are transmitted using carriers of differentfrequencies.

In the transmission method of FIG. 12 also, the downlink qualityinformation and the uplink pilot signal can be transmitted out in adistributed manner. In the distributed transmission method, thebandwidth of each carrier is narrow, but since the carriers are widelydistributed, the frequency bandwidth that the entire signal uses iswide. As a result, when the downlink quality information and the uplinkpilot signal are transmitted using different frequency bands, thedifference between the transmission frequencies of these control signalsmay become substantial, increasing the processing complexity of theradio transmitting unit 212 as earlier described.

To prevent the difference between the carrier frequencies of thedownlink quality information and the uplink pilot signal from becomingsubstantial, in the transmission method of FIG. 12 the inverse Fouriertransform circuit 234 selects adjacent carrier frequencies from amongthe carrier frequencies assigned to the mobile user terminal (UE), andassigns the thus selected adjacent carrier frequencies for thetransmission of the uplink pilot signal and the downlink qualityinformation, thereby preventing their transmission frequencies frombecoming substantially different from each other.

The downlink quality information and the uplink pilot signal may betransmitted out in a so-called localized manner. The inverse Fouriertransform circuit 234 may select, from among the plurality of carrierfrequencies lying within the given frequency band assigned to the mobileuser terminal (UE), some of the carrier frequencies clustered in alocalized manner within the given frequency band and may assign the thusselected carrier frequencies for the transmission of the downlinkquality information and the uplink pilot signal. FIGS. 13 and 14 aretime charts each showing an example of how the downlink qualityinformation and the uplink pilot signal are transmitted out in alocalized manner.

In the example of FIG. 13, the uplink pilot signal is transmitted duringtime periods t1 to t2 and t4 to t5, and the downlink quality informationduring time periods t2 to t3 and t5 to t6, using some of the localizedcarrier frequencies selected from among the plurality of carrierfrequencies lying within the given frequency band assigned to the mobileuser terminal (UE). Here, the uplink pilot signal and the downlinkquality information are transmitted using carriers of the same frequencyand at the same intervals of time.

In the example of FIG. 14, the uplink pilot signal and the downlinkquality information are transmitted at the same time by using some ofthe localized carrier frequencies selected from among the plurality ofcarrier frequencies lying within the given frequency band assigned tothe mobile user terminal (UE) during time periods t1 to t2 and t3 to t4.Here, the carrier frequencies used for the transmission of the uplinkpilot signal and the downlink quality information are adjacent to eachother, as in the transmission method shown in FIG. 9.

The transmit time control unit 216 may set the transmission cycle ofeither one of the uplink pilot signal and the downlink qualityinformation to an integral multiple of the transmission cycle of theother so that the respective control signals are transmitted out atdifferent time intervals. For example, in the transmission method shownin FIG. 15, the transmission cycle of the uplink pilot signal is made tooccur at twice the frequency of the transmission cycle of the downlinkquality information, while in the transmission method shown in FIG. 16,the transmission cycle of the downlink quality information is made tooccur at twice the frequency of the transmission cycle of the uplinkpilot signal.

In this way, the amount of information to be transmitted within a givenperiod, for example, can be made different between the uplink pilotsignal and the downlink quality information, or the ratio between thefrequency bands used for the transmission of the uplink pilot signal andthe downlink quality information can be varied as desired.

The radio transmitting unit 212 may use different frequency bands forthe transmission of the uplink pilot signal and the downlink qualityinformation in order to make the amount of information to be transmittedwithin a given period different between the uplink pilot signal and thedownlink quality information. In the transmission method shown in FIG.17, frequency band Δfc which is larger than frequency band Δfp used forthe transmission of the uplink pilot signal is used for the transmissionof the downlink quality information, while in the transmission methodshown in FIG. 18, frequency band Δfc which is smaller than frequencyband Δfp used for the transmission of the uplink pilot signal is usedfor the transmission of the downlink quality information.

When the mobile user terminal (UE) transmits the downlink qualityinformation and the uplink pilot signal at the same time or at timesclose to each other by using the same frequency or adjacent frequenciesas described above, the radio receiving unit 112 in the base station BSshown in FIG. 4 can use the uplink pilot signal as a reference channelfor channel estimation for the downlink quality information.

FIGS. 19A and 19B are diagrams each showing a configuration example ofthe radio receiving unit 112 in FIG. 4, as shown, the radio receivingunit 112 includes a channel estimating unit 136 which performs channelestimation for the downlink quality information by using the uplinkpilot signal as a reference channel.

When the radio transmitting unit 212 in the mobile user terminal (UE)is, for example, an OFDM transmitter such as shown in FIG. 10A or 10B,the radio receiving unit 112 in the base station BS may be an OFDMreceiver such as shown in FIG. 19A or 19B.

The radio receiving unit 112 comprises: a frequency conversion circuit131, which converts the radio frequency signal received by the antenna121 into an intermediate frequency signal; a quadrature detectioncircuit 132, which quadrature-detects the intermediate frequency signal;analog-digital conversion circuits 133 and 134, which converts theanalog quadrature signals output from the quadrature detection circuit132 into digital quadrature signals; a Fourier transform circuit (FFT)135, which demodulates the downlink quality information and the uplinkpilot signal from the digital quadrature signals; and parallel-serialconversion circuits 138 and 139, which convert the demodulated downlinkquality information and uplink pilot signal into serial signals foroutput to the first and second control channel receiving units 113 and114, respectively.

In the block diagrams of FIGS. 19A and 19B, only the portions necessaryfor receiving the uplink pilot signal and the downlink qualityinformation are shown, however, the radio receiving unit 112 furtherincludes component elements necessary for the reception of other controlsignals, packet data, and voice data.

The radio receiving unit 112 further comprises: the channel estimatingunit 136, which uses the uplink pilot signal output from the Fouriertransform circuit 135 as a reference channel and thereby outputs acorrection signal for compensating for variations that occurred in thetransmission path of the uplink pilot signal; and a multiplying circuit137, which multiplies the downlink quality information output from theFourier transform circuit 135 by the correction signal output from thechannel estimating unit 136.

FIG. 19A shows the configuration of the radio receiving unit 112 for acase where the uplink pilot signal and the downlink quality informationare transmitted using carriers of different frequencies. In thisconfiguration, the uplink pilot signal and the downlink qualityinformation are respectively output from different terminals of theFourier transform circuit 135; the serial-parallel conversion circuit138 is connected to the terminal at which the downlink qualityinformation is output, and the serial-parallel conversion circuit 139 isconnected to the terminal at which the uplink pilot signal is output. Inthis way, downlink quality information is supplied to the first upstreamcontrol channel receiving unit 113, and the uplink pilot signal issupplied to the second upstream control channel receiving unit 114.

FIG. 19B shows the configuration of the radio receiving unit 112 for acase where the uplink pilot signal and the downlink quality informationare transmitted using carriers of the same frequency. In thisconfiguration, the uplink pilot signal and the downlink qualityinformation are output from the same terminal of the Fourier transformcircuit 135. Therefore, the radio receiving unit 112 includes a switch140, which operates to couple the output signal of the Fourier transformcircuit 135 to the serial-parallel conversion circuit 138 during thereception of the downlink quality information and to the serial-parallelconversion circuit 139 during the reception of the uplink pilot signal.

The transmit time information generating unit 106 determines thereceiving times for the uplink pilot signal and the downlink qualityinformation in accordance with the transmit time information created fortransmission to the mobile user terminal (UE). Then, a switching controlsignal is generated that causes the switch 140 to perform the aboveswitching operation.

The switch 140 directs the output signal of the Fourier transformcircuit 135 to the designated serial-parallel conversion circuit 138 or139 in accordance with the switching control signal, thus supplying thedownlink quality information to the first upstream control channelreceiving unit 113 or the uplink pilot signal to the second upstreamcontrol channel receiving unit 114.

In accordance with the switching control signal output from the transmittime information generating unit 106, when the uplink pilot signal isreceived the channel estimating unit 136 uses the uplink pilot signaloutput from the Fourier transform circuit 135 as a reference channel andthereby generates the correction signal for compensating for variationsthat occurred in the transmission path of the uplink pilot signal. Whenthe downlink quality information is received, the output signal of theFourier transform circuit 135 is multiplied in the multiplying circuit137 by the correction signal to correct the downlink qualityinformation.

FIG. 20 is a flowchart showing the channel estimation operation for thedownlink quality information performed by the base station BS.

In step S11, the radio receiving unit 112 receives the uplink pilotsignal transmitted over the second upstream control channel from themobile user terminal (UE), and at the same time, receives the downlinkquality information transmitted over the first upstream control channelusing a carrier frequency that is adjacent to the carrier frequency ofthe uplink pilot signal. Alternatively, the radio receiving unit 112receives the uplink pilot signal transmitted over the second upstreamcontrol channel from the mobile user terminal (UE), and at a time closeto the receipt time, receives the downlink quality informationtransmitted over the first upstream control channel using a carrierfrequency that is the same as or adjacent to the carrier frequency ofthe uplink pilot signal.

In step S12, the channel estimating unit 136 performs channel estimationfor the first upstream control channel by using the uplink pilot signaloutput from the Fourier transform circuit 135 as a reference channel,and generates a correction signal for the downlink quality information.

In step S13, the channel estimating unit 136 corrects the downlinkquality information output from the Fourier transform circuit 135, bymultiplying the downlink quality information with the correction signalby using the multiplying circuit 137.

According to the present invention, since the downlink qualityinformation and the uplink pilot signal can be transmitted at the sametime or in successive time periods, the number of times that power isturned on to the amplifier circuit provided in the output stage of thetransmitter circuit of the mobile user terminal decreases, andconsequently, the length of time that the amplifier circuit has to beenergized before the transmission of the signal is reduced, thusreducing the power consumption.

Furthermore, since the downlink quality information and the uplink pilotsignal can be transmitted using the same carrier frequency or carrierfrequencies close to each other, it is possible to reduce the amount ofbias control to be applied to the amplifier circuit provided in theoutput stage of the transmitter circuit of the mobile user terminal, andthus the processing complexity of the transmitter circuit can beprevented from increasing.

The present invention can be applied widely to a mobile user terminal, amobile communication system, and a base station wherein downlink qualityinformation and an uplink pilot signal are transmitted from the mobileuser terminal to the base station. In particular, the invention can beapplied advantageously to a mobile user terminal, a mobile communicationsystem, and a base station that employs the 3.9-generation mobilecommunication architecture for which standardizing is currentlyunderway.

While the invention has been described with reference to specificembodiments chosen for purpose of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention.

1. A mobile user terminal comprising: a receiver which receives asignal; and a processor which measures downlink channel quality based onthe signal and does not transmit downlink channel quality informationand an uplink pilot signal simultaneously at a period which the mobileuser terminal is a state of transmission off in an intermittent fashion.